A neglected field has been the study of how conditioning contributes to human locomotion. The proposed investigation will study operant (discriminative) control for electromyographic and kinematic responses as people walk on a motor-driven treadmill. The effect on other muscles will be noted as one muscle is controlled, and the relative modifiability of control for different components of the step cycle can be examined. A response that is resistant to change may indicate obligatory, built-in reflex mechanisms. One major aim of the work is to establish and manipulate public discriminative control, to help us understand cooperation or competition between muscles of different actions or at different joints--when they are controlled separately or together. Computer programming will deliver lights, test for successfulness of the subsequent response, and deliver the appropriate consequence (tone), depending upon whether or not the EMG burst was successful. A second major aim is to look for presumptive "movement-produced" stimulation--private events, such as stretches or tensions applied to muscles, that excite proprioceptors. It is postulated that these events acquire discriminative control early in life, although it may be poorly developed in many people, and that we may unveil their actions by systematically eliminating the public tones and lights used for the first aim. The second aim will determine durability and, to some extent, bodily location of private control. It will also find out whether or not people have "movement sense" to correctly identify responses as successful or not. Results as a whole will begin to establish the specific behavioral mechanisms--reflexive or conditioned--through which postulated "rhythm generator" cells in the nervous system are activated. Findings will be useful for those who teach control and self-control of locomotion to the motorically handicapped person or to "normal" individuals who seek to improve their walking or running.